High speed electronic circuits, such as microwave amplifiers and sub-nanosecond logic, often employ differential circuitry, and consequently operate with push-pull input signals. In some instances, such circuitry requires not just one push-pull input signal, but two or more, each with equal amplitudes.
Conventional signal sources have single-ended outputs. To convert single-ended signals into two or more equal amplitude push-pull signals, an arrangement including a balun cascaded with two power splitters (FIG. 1), or a power splitter cascaded with two baluns (FIG. 2), may be used. Unfortunately, conventional power splitters only deliver one-fourth the input power to each of the two outputs. (The remaining half of the input power is dissipated in internal impedance matching resistors.) This loss, coupled with the losses associated with the balun(s), typically leaves less than 45 percent of the input signal for application to the circuitry.
High frequency signal power is always at a premium, so it is desirable to minimize the above-described losses.
In accordance with the present invention, a dual output balun distributes all the signal power applied to the balun, less small parasitic losses, equally to two (or more) push-pull output paths, thereby providing about a 7 dB improvement in efficiency over conventional balun and power splitter approaches. The balun includes a single ended input port for receiving a single ended input signal, two balanced, push-pull output ports, and a transformer: (a) for receiving a single ended input signal from the input port; (b) converting the single ended input signal into a pair of balanced output signals; and (c) and providing the output signals to the output ports.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.